526 Progress in Science. [October, 
formed being for the most part the ‘‘ cap-stone,’’ which covers the valuable 
Portland stone, but which of itself is valueless, except for this purpose. 
The total length of the whole work is about 13 miles, the width of the 
structure at the base being 300 feet, at low-water level from go to roo feet, 
and at the top 60 feet. The average height from the bottom is 70 feet. The 
sheltered area afforded by these works is about 2100 acres in extent up to 
low-water line. Connected with the works are two forts, an inner and an 
outer one, placed one at the end of the pier and the other at the end of the 
breakwater proper. The inner fort is 100 feet in diameter, mounts 8 guns, 
and stands in g} fathoms of water. The outer fort, on the North Head, has a 
rubble base, 45 feet high, and containing 140,000 tons of stone. The diameter 
of the fort is 200 feet, and it stands in 10 fathoms of water. 
Vienna Exhibition.—On the 1st of May, in next year, an Universal Exhibi- 
tion is to be held at Vienna, which, from the dimensions proposed to be given 
to the building, bids fair entirely to eclipse all former Exhibition buildings, the 
space devoted for it being no less than 2,783,809 square yards. These propor- 
tions will be better appreciated by a comparison with the areas covered by 
former Exhibitions, which were as follows :— 
London (Hyde Park), 1851 .. .. =~. 94,000 square yards. 
Parish (Champs Ely Sees) i:555 1-eaectomnne e232) es a 
London (Brompton), 1862 Bo 0D (ou ae ee 
Paris (Champ de Mars), 1867... .. .. 527,645 ,, e 
The design for the Vienna Exhibition building is due, we understand, to 
Mr. Scott Russell. The central part of the building consists of an imposing 
iron rotunda, or dome, with an outside diameter of 353°68 feet, and a height 
of 275°5 feet. A conical iron roof, rising to a height of 158-0g feet, is sup- 
ported by 31 iron columns, each 79’99 feet in height. This conical roof carries 
an iron lantern, having an outside diameter of 10627 feet, and a height of 
32°8 feet up to the roof, which latter rises 24°27 feet. Upon this is placed 
another structure, 26°2 feet in diameter and 60°6 feet high. The whole space 
covered by the rotunda has an outside circumference of 1111°20 feet, whilst 
the inside circumference is 1038°28 feet, having an available space of 9722°28 
square yards. The rotunda communicates with the main gallery, or nave, 
which has a width of 82 feet and a total length of 2968-4 feet: this nave is 
crossed, at equal distances, by 16 cross naves, 49°2 feet wide and 672-4 feet 
long, creating thus, at both sides of the main gallery, 24 courts, which are 
enclosed at three sides, and which have the same length as the cross nave and 
a width of 114°8 feet. 
MEETINGS OF SOCIETIES. 
Mechanical Engineers.—The Institution of Mechanical Engineers held their 
Annual Meeting at Liverpool, under their President, Mr. C. W. Siemens, on 
the 30th of July last and following days. In his Address the President re- 
ferred principally to the question of economy of fuel, which, in the presence 
of ever-increasing demand and of failing supply, is rapidly rising into a 
question of national importance; and he remarked that it would not be diffi- 
cult to prove that—in almost all the uses of fuel, whether to the production of 
force, to the smelting and re-heating of iron, steel, copper, and other metals, 
or to domestic purposes—fully one-half of the present enormous.consumption 
might be saved by the general adoption of improved appliances which are 
within the range of our actual knowledge. 
The papers read at this meeting were as follows, but space will not admit 
of any more full reference regarding them :— 
1. “On the Progress effetted in Economy of Fuel in Steam Navigation, 
considered in Relation to Compound Cylinder Engines and High- 
Pressure Steam,” by Mr. F. J. Bramwell. 
2. “*On the Application of Water Pressure to Shop Tools and other En- 
gineering Works,” by Mr. Ralph Hart Tweddell. 
3. ** Description of Coal-Cutting Machinery with Rotary Cutter, worked by 
Compressed Air,” by Mr. Robert Winstanley. 
